Topic: 1978 CB550k

[Jonesy_10]

Hey guys. I'm 17 years old, living in Ontario, Canada.

I just finished my first riding season on a 1978 Yamaha XS400 that I restored (with the help of my dad).



Anyway, for my second riding season, I wanted something a little bigger, more comfortable, more powerful. To make a long story short, I ended up buying my dad's CB550k off him.



That picture was from this spring; the bike needs some work. Over the summer, it acquired a few problems. Firstly, the head gasket is leaking badly, as well as the oil pan gasket, so I figure the engine might as well be stripped, and a full gasket set put in.

Secondly, actually a slightly strange problem; the bike has blown 3 rear tubes this summer. One of them was actually thicker and stronger than the usual ones. The rim has been inspected a few times and the rim tape has been replaced, but it's in good shape. At this point, we think the tyre might just be too big. If I recall correctly, it's a 120/90 18 Spitfire. Maybe we should stick to the original size. Any thoughts?

Lastly. The exhausts have started rotting at the ends. Hard to see in the picture, but they are very bad on the bottom. We even welded over them to try to patch them, but the mufflers need replacing. Any thoughts? Should I buy a 4 into 2? 4 into 1? Do I need to rejet the carbs? Or do I buy some slip on mufflers?

Any input would be great. Thanks!

[Tom in Newcastle......Ontario]

Hi from Newcastle On.I also have a 78 550k

Where in Ontario are you ?

For the oil leak do a search or two,lots of good info..

I have a spare set of OEM pipes,they are not mint(#4 has a patch,bottom of the header,) but might be better then yours.

[Deltarider]

That's a K4. First one I see. Original tire size is best: front 3.25-19, rear 3.75-18 or 4.00-18. Original mufflers are hard to find, if not impossible. Some Italian and/or Spanish manufacturers (Sito, Mecadapo, Busso) did 4-4 slip ons. Sito looked like this: http://www.echappementmoto.com/IMAGES/echappementmoto/HONDA/CB%20750%20K7/echappement%20moto%20HONDA%20CB%20750%20K7.htm
Mecadapo looked like this: http://www.cmsnl.com/community/vehicles/Honda/CB_550_K3/1978/1910.html
MIVV looked like this:

If you can't find them, I would go for 4-2 slip ons. That bike deserves the looks of at least a 4-2. Sito had them. Do not start to rejet at once. On the other hand with any aftermarket exhaust I think it will be hard to avoid #100 main jets, since the K3 and K4's were set to lean anyway. Probably no further modifications will be needed.

Firstly, the head gasket is leaking badly, as well as the oil pan gasket, so I figure the engine might as well be stripped, and a full gasket set put in.

Maybe you should wait with that. 1. All 500/550's leak. 2. Yours probably sat a long time. I would begin with riding it regularly and see how it develops. Maybe leakages diminish, once gaskets have swollen somewhat again. Maybe. Be nice when coldstarting it. Do not rev it higher than 2500. Gently let it warm during the first 10 - 15 km's. These bikes are coldblooded. When the engine is hot, you can do anything you want with it.

[trifistus]

I am looking for a set of exhausts as well for my 78 K4...every now and again, someone will sell a set they dug out of a wherehouse somewhere on eBay, but that is rare (i've seen it exactly twice in the past year) and if you can find them, it seems that the going rate is about 895 USD...kind of cost prohibitive.

I am actually looking at a set of "brand new" old 4 into 2s for a CB 550F...does anyone know if these will fit on the K model?  I am assuming that the frame and mount points are exactly the same, so it would stand to reason that these would fit. 

Failing that, does anyone have any recommendations about a reasonable aftermarket exhaust?  I've seen the MAC Performance exhausts and they do not excite me.

cheers!

[Jonesy_10]

Hi tjjkc, I'm in Brighton, Ontario. PM sent!

And to Deltarider,

My dad rode the Honda all summer, and the leak has been getting progressively worse. It's now at a point where a few pairs of my dad's jeans have permanent oil stains on them...

[OldSchool_IsCool]

There are a couple of rubber disks under the tappet cover that often leak.  Those could be the source of the oil.  Fairly easy fix and doesn't require pulling the engine out of the frame nor taking the head off.

[Jonesy_10]

Alright. So now I have two original exhaust systems. The set on the bike are rotting on the outside, however have good baffles in them.

The other set I have look nice on the outside, but have no baffles in them.

Would it be possible to grind the good baffles out and put them in the nicer pipes? Or tjjkc said he had heard about putting copper piping in instead?

Any thoughts?

[Tom in Newcastle......Ontario]

Hi Gareth

Must of been a misunderstanding,(or too many people talking at the same time), on those pipes you bought from me....

I did not say use copper pipe ,I mentioned that I have heard that some people have ground out the old baffles and welded in a pipe that had a bunch of holes drilled in .......


Just thought that I would clear that up .........no need to get some people confused or on the warpath

[Jonesy_10]

Sorry, my bad. Thanks for clearing it up!